1. Field of the Invention
The present invention relates to a europium-activated oxynitride phosphor and a light emitting device using the same.
2. Description of the Related Art
While it is an oxide or sulfide that has since been used as a phosphor, a new phosphor such as a nitride or oxynitride phosphor has attracted a lot of attention and inspired vigorous researches in recent years.
Among the oxynitride phosphors that have been conventionally used, there is a divalent-activated Ca-alpha-SiAlON phosphor (See Japanese Patent Application Laid-open Publication No. 2002-363554, for example). The Ca-alpha-SiAlON phosphor is referred to simply as SiAlON phosphor, when appropriate, hereinafter.
The SiAlON phosphor can be used for example as a wavelength conversion material for a white light emitting diode (white LED) equipped with a blue light emitting diode chip (blue LED) as an excitation light source.
The above white light emitting diode has drawn attention as a next-generation highly efficient lighting apparatus substituting a conventional incandescent or fluorescent lamp and attracted active investigations on such a diode.
Among several types of white light emitting diodes developed to date, the mainstream white light emitting diode is configured to have a blue light emitting diode chip as an excitation light source and a phosphor for converting a wavelength of part of blue light emitted from the blue light emitting diode chip into a different wavelength, thereby emitting white light as a result of color mixture of blue light from the blue light emitting diode chip and the wavelength-converted yellow-light.
In order to improve luminous efficacy and intensity in a light emitting device including such a white light emitting diode of wavelength conversion type, there has to be improved not only the blue light emitting diode chip as an excitation light source but also a conversion efficiency of the phosphor.
While the SiAlON phosphor is suitable as a wavelength conversion material for the white light emitting diode of such a type, a further improvement in luminous efficacy and intensity have been desired.